Metalized ceramic leading edge nozzle kiels for high-temperature turbine applications

ABSTRACT

A pressure probe includes an elongated cable provided with a sensing tip, a portion of the elongated cable and sensing tip enclosed within a ceramic shroud, the ceramic shroud at least partially formed of a metalized ceramic material.

BACKGROUND OF THE INVENTION

This invention relates generally to gas turbine monitoring and testingpractices and, more specifically, to a metalized ceramic Kiel-typepressure sensor used to gather total pressure and/or total temperaturedata from the surrounding flow in the hot gas path of a turbine engine.

Kiel-type pressure sensor probes are often used to measure totalpressure in a fluid environment where the direction of flow is not knownor changes with operating conditions. Associated pressure tubingconnects the probe to a transducer where the pressure measurement istranslated to a signal for routing to a data acquisition system. TheKiel-style probe has a shroud to protect the pressure tubing. The shroudmakes the probe insensitive to a range of yaw and pitch angles becausethe flow is straightened as it enters the probe. Kiel-style probes canbe installed in a variety of turbine components/locations, for example,in a low-pressure steam-turbine exhaust duct, enabling measurement ofthe total pressure distribution exiting the last-stage row of bucketsduring performance testing. U.S. Pat. No. 4,433,584 exemplifies the useof a plurality of Kiel-style probes (referred to hereinafter as “Kielprobes”) on a rake downstream of a turbine section. In addition, Kielprobes are sometimes mounted in the hot gas path of the turbine. i.e.,on components of the gas turbine that are contacted by the hotcombustion gases, especially in the first and second stages of the gasturbine.

Traditional Kiel probe shrouds or housings used in gas turbineapplications, and especially those mounted on nozzles in the hot gaspath, have been made from high-temperature alloys. Even thesehigh-temperature alloys, however, cannot withstand the temperature inthe first stage and sometimes even in the second stage of modern gasturbines where temperatures can reach 2300° F. Unless active coolingschemes are employed to cool the metal alloy shrouds, the shrouds maywell disintegrate under the extremely high temperatures. While platinumis an option for the shroud composition, it is very expensive and thusrarely if ever used in Kiel probe applications.

Ceramic materials, while able to withstand the high temperatures in thehot gas path of the gas turbine, are difficult to bond to the host metalalloy nozzle or other metal alloy turbine component.

There remains a need therefore, for a relatively low-cost Kiel probeshroud construction that will survive the high-temperature environmentof a gas turbine hot gas path.

BRIEF SUMMARY OF THE INVENTION

In accordance with an exemplary but nonlimiting embodiment, there isprovided a pressure probe comprising an elongated cable provided with asensing tip, a portion of the elongated cable and the sensing tipenclosed within a ceramic shroud, the ceramic shroud having at least aportion thereof metalized to facilitate bonding to a metal component.

In another aspect, the present invention provides pressure probeassembly capable of withstanding temperatures up to about 2300°comprising at least one pressure probe secured to a component, thepressure probe comprising an elongated cable provided with a sensingtip, a portion of the elongated cable and the sensing tip enclosedwithin a silicon carbide ceramic shroud, the silicon carbide ceramicshroud having at least a portion thereof metalized; the metalizedportion of the silicon carbide ceramic shroud brazed to the metalcomponent.

In still another exemplary but nonlimiting aspect, the present inventionprovides a pressure probe assembly capable of withstanding temperaturesup to about 2300° comprising at least one pressure probe secured to ametal alloy gas turbine hot gas path component, the pressure probecomprising an elongated cable provided with a sensing tip, a portion ofthe elongated cable and the sensing tip enclosed within a siliconcarbide ceramic shroud, the silicon carbide ceramic shroud having atleast a portion thereof metalized; the metalized portion of the siliconcarbide ceramic shroud brazed to the metal alloy gas turbine hot gaspath component.

The invention will now be described in greater detail in conjunctionwith the drawings identified below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a metalized ceramic Kiel probe inaccordance with a first exemplary but nonlimiting embodiment of theinvention;

FIG. 2 is a perspective view of a metalized ceramic Kiel probe fittedwith a sleeve or adaptor about the metalized portion of the probe;

FIG. 3 is a longitudinal section view of the Kiel probe shown in FIG. 2;

FIG. 4 is perspective view of a gas turbine nozzle to which is attacheda plurality of metalized ceramic Kiel probes of the type shown in FIG.1;

FIG. 5 is a perspective view of a pressure sensor rake mounting ametalized ceramic Kiel probe in accordance with another exemplary butnonlimiting embodiment; and

FIG. 6 is a partial perspective view of a gas turbine transition pieceinto which a pressure sensing rake of the type shown in FIG. 3 has beeninserted and bonded.

DETAILED DESCRIPTION OF THE INVENTION

With initial reference to FIG. 1, the Kiel probe 10 includes a shroud orhousing 12 enclosing a pressure-sensing cable or tubing, represented at14, with a sensing tip represented at 16 located at or adjacent theouter end of the shroud or housing 12. Typically, one or more transverseapertures 18 are formed in the shroud or housing to enable any moisturegathering in the shroud to drain from the shroud so as not to negativelyimpact the accuracy of the Kiel probe.

It will be understood that the pressure sensing cable or tubing 14 andthe pressure-sensing tip 16 form no part of the invention in that theyare well-known in the art. This invention has to do with the compositionof the shroud or housing 12 of the Kiel probe 10 and the manner in whichthe Kiel probe shroud or housing is attached to a metal turbinecomponent or a metal instrumentation rake as described further below.

In accordance with an exemplary but nonlimiting embodiment of theinvention, the Kiel probe shroud or housing 12 is formed of ahigh-temperature ceramic material. In order to bond the ceramic Kielprobe shroud or housing to a metal component, at least a portion of theceramic shroud indicated at 20 in FIG. 1, is metalized to facilitatebonding the probe to a metal turbine component or instrumentation rake.

In the exemplary embodiment, the Kiel probe shroud or housing 12 iscomprised of silicon carbide (Sic). More specifically, it has been foundthat silicon carbide not only withstands the high-pressure/temperatureenvironment of a turbine engine hot gas path, but also is easilymachined. In addition, a portion of the SiC shroud can be laced with ametal alloy so that the shroud can be bonded with a metal alloy turbinecomponent or pressure-sensing rake. The entire length of the Kiel probeshroud need not be metalized. It is only required that the metalizedportion be of sufficient extent to enable the desired bonding with themetal alloy component or device to which the Kiel probe is to beattached. Thus, an axially-extending portion 20 of the substantiallycylindrical silicon carbide Kiel probe shroud or housing 12 shown inFIG. 1, representing about 30-50% of the length of the shroud, can bemetalized by any conventional and known metallization process, forexample, vapor deposition, vacuum heat furnace/thermal spraying, activemetallization, etc. The metal used in the metallization process isapplication and host material specific. In many turbine-relatedapplications, the host material is a high temperature Nickel alloy, butCobalt alloys are sometimes employed as well.

While the probe 10 has been shown to have a right-cylinder shape, it mayhave other shapes such as tapered or conical, etc. along all or part ofits length dimension.

In an exemplary but non-limiting embodiment, and as best seen in FIGS. 2and 3, a metal sleeve or adaptor 22 may be formed and coated on itsinterior with a glass fiber composite. After the metal sleeve 22 isinserted over a portion (e.g., portion 20) of the ceramic Kiel probeshroud or housing 12, it is molecularly bonded under high heat to theunderlying SiC material, thus creating the desired metalized ceramicportion 20 that can be more easily bonded to a metal turbine hot gaspath component or metal instrumentation rake. The preferred method bywhich the Kiel probe housing 12 is bonded to the turbine component orinstrumentation rake is brazing. The resultant Kiel probe assembly canwithstand temperatures up to about 2300° F. typically experienced inmodern gas turbine combustors.

FIG. 4 shows one application for the metalized ceramic Kiel probe 10 ofFIG. 1. Here, two such Kiel probes 22 and 24 are brazed within aperturesprovided in a stationary gas turbine nozzle 26. It will be appreciatedthat the number, location and/or pattern of Kiel probes on anyparticular hot gas path component is within the skill of the art.

FIG. 5 illustrates another application for the metalized ceramic Kielprobe 10, where the metalized portion 20 of the Kiel probe shroud orhousing 12 is brazed to a metal alloy sensor rake 28 that, in turn, maybe located so as to project into an aft portion of a gas turbinetransition piece 30 (see FIG. 4) which feeds hot combustion gases to theturbine first stage.

In one exemplary but nonlimiting example, the host metal alloy maycomprise Inconel 718, and the host component may be a turbine nozzle orother stator component, a turbine exhaust duct, or an instrumentationrake (or other instrumentation support or holder) secured to an exhaustduct or other turbine structure, e.g. a combustor transition piece asshown in FIG. 6. As noted above, the Kiel probe shroud 12 is composed ofSiC, and the metal used in the metallization process is a nickel/silveralloy with silicon added. In this example, the metallization processcomprises an active metallization in a one-step vacuum heat treat thatmolecularly bonds the metallization material to the ceramic. The sleeveor adaptor 22 may be composed of a nickel-chromium based superalloy suchas Inconel 718, or other suitable metal, and the subsequent brazing ofthe probe sleeve to the host component is carried out at a temperatureof about 2175° F. A suitable braze material is PALCO (1219° C. Eutectic65PD-35CO alloy).

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A pressure probe comprising an elongated cableprovided with a sensing tip, a portion of said elongated cable and saidsensing tip enclosed within a ceramic shroud, said ceramic shroud havingat least a portion thereof metalized to facilitate bonding to a metalcomponent.
 2. The pressure probe of claim 1 wherein said ceramic shroudcomprises silicon carbide.
 3. The pressure probe of claim 1 wherein saidshroud is provided in the form of an elongated cylinder with at leastone open end.
 4. The pressure probe of claim 3 wherein said metalizedportion of said shroud comprises about 30-50% of a length of saidelongated cylinder.
 5. The pressure probe of claim 4 whereinmetallization of said portion is carried out with a silver/nickel alloywith silicon added.
 6. The pressure probe of claim 5 wherein said alloyis molecularly bonded to said ceramic shroud.
 7. A pressure probeassembly capable of withstanding temperatures up to about 2300°comprising at least one pressure probe secured to a component, saidpressure probe comprising an elongated cable provided with a sensingtip, a portion of said elongated cable and said sensing tip enclosedwithin a silicon carbide ceramic shroud, said silicon carbide ceramicshroud having at least a portion thereof metalized; the metalizedportion of said silicon carbide ceramic shroud brazed to said metalcomponent.
 8. The assembly of claim 7 wherein said component comprises aturbine nozzle.
 9. The assembly of claim 7 wherein said componentcomprises a metal instrumentation rake.
 10. The assembly of claim 7wherein said component comprises a turbine combustor transition piece.11. The assembly of claim 7 wherein said ceramic shroud is comprised ofsilicon carbide and said portion is metalized with a nickel/silver alloywith silicon added.
 12. The assembly of claim 7 wherein said componentis comprised of a nickel alloy.
 13. A pressure probe assembly comprisingat least one pressure probe secured to a metal alloy gas turbine hot gaspath component, said pressure probe comprising an elongated cableprovided with a sensing tip, a portion of said elongated cable and saidsensing tip enclosed within a silicon carbide ceramic shroud, saidsilicon carbide ceramic shroud having at least a portion thereofmetalized; the metalized portion of said silicon carbide ceramic shroudenclosed within a sleeve and brazed to said metal alloy gas turbine hotgas path component.
 14. The pressure probe assembly of claim 13 whereinsaid metal alloy gas turbine hot gas path component comprises a turbinenozzle.
 15. The pressure probe assembly of claim 13 wherein said metalalloy gas turbine hot gas path component comprises a gas turbine exhaustduct.
 16. The pressure probe assembly of claim 13 wherein said metalalloy gas turbine hot gas path component comprises a turbine combustortransition piece.
 17. The pressure probe assembly of claim 13 whereinsaid portion is metalized with a nickel/silver alloy with silicon added.18. The pressure probe assembly of claim 13 wherein said metalizedportion comprises 30-50% of a length dimension of said silicon carbideceramic shroud.
 19. The pressure probe assembly of claim 18 wherein saidsleeve is comprised of a nickel-chromium based superalloy.
 20. Thepressure probe assembly of claim 13 wherein said alloy gas turbine hotgas path component is composed of a high-temperature nickel alloy.